Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat May 27 2023 22:03:37 AWUS01 KWNH 272203 FFGMPD NEZ000-SDZ000-MTZ000-WYZ000-280300- Mesoscale Precipitation Discussion 0359 NWS Weather Prediction Center College Park MD 602 PM EDT Sat May 27 2023 Areas affected...Eastern WY...Far Southeast MT...Western SDak... Concerning...Heavy rainfall...Flash flooding possible Valid 272200Z - 280300Z SUMMARY...Initially slow moving cells ahead of height-falls and potential for repeats/mergers poses localized 2-3" totals and possible flash flooding. DISCUSSION...GOES-E Visible/EIR denotes numerous stronger thunderstorms/overshooting tops developing along the North Laramie Range arched ahead of sharp 500-300mb trough axis and entrance to 3H jet streak over the High Plains of NE WY/E MT. At the low levels, strong southerly and southeasterly flow has been pumping unstable (2000+ MLCAPEs) higher theta-E air into the region/directed near the Black Hills. As such, stronger convergence along/east of the frontal zone has resulted in scattered very strong updrafts across northeast WY into SE MT as well, ahead of the main upper-level height-falls.=20 Surface Tds are in the mid to upper 50s, but the overall moisture profile is fairly dry aloft with total PWats at 1-1.25", as such, moisture flux convergence will be critical for favorable rainfall production. Moderate effective bulk shear values suggest some rotating updrafts for storm mode to support enhanced isallobaric moisture flux into the updraft and given updraft strength, this should help with rainfall production. Inflow of 20-30kts at cloud base should support rates up to 2"/hr, but duration at a location will be critical as well.=20 Currently, precursory development across Weston and Crook/Butte counties are likely to be very slow initially as low level profiles are responding more to the approaching line/height-falls this should allow for increased duration for localized 2-3" totals possible with the severe hail. Given FFG values are low (less than 1.5"/hr and less than 2"/3hrs), scattered flash flooding is considered possible. Additionally, as the faster moving cells lift north and east on the height-falls, there is increasing potential as for cell mergers and upscale growth of the complex for potential repeating/short-term enhanced sub-hourly rates that would result in very little absorption/increased runoff. Eventually, forward propagation along building broad outflow boundary/squall line will limit duration of these intense rates limiting totals to 1-2" crossing higher FFG values of W South Dakota into adjacent NW Nebraska/SW North Dakota reducing the flash flooding risk.=20 Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7BlM__g2p3PgebHJ55vy79Ohy1K3RQZc2k8dEDOyNTwRvuQlRIPbhgXfGXWSsQbrDIhD= Bx2M-OLFTbealoCxNqMITNc$ for graphic product... ATTN...WFO...BYZ...CYS...UNR... ATTN...RFC...MBRFC...NWC... LAT...LON 45950428 45720346 44810300 43610309 42060409=20 41740542 43760597 45130588 45900527=20 =3D =3D =3D To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM. --- SBBSecho 3.14-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .